Mr. Bell presents with the inability to move certain muscles on one side of his face. You ask him to make various facial express
ions and find that on his right side he is unable to purse his lips, pull in his cheeks, elevate his upper lip, and smirk. What muscles is Mr. Bell unable to contract?
Voluntary muscles (also named red muscles and striated muscles) are attached to the skeleton and bones, and they are required for the essential movement and locomotory functions. In these muscles, the contraction is controlled by the brain (i.e., voluntary contraction). Facial striated muscles (also known as mimetic muscles) are supplied by the facial nerve and control facial expression.
Myasthenia gravis is a disease that affects voluntary muscles. This disease is associated with the inability to move voluntary muscles (in this case, face paralysis).
